BOSTON, Massachusetts—Noninvasive, transcranial direct current stimulation (tDCS) significantly reduced fibromyalgia (FM) pain in a sham-controlled pilot study, confirming that FM is a central pain syndrome and should be tested in larger trials, Felipe Fregni, MD, and colleagues report in Arthritis & Rheumatism.¹

Dr. Fregni's team randomized 32 FM patients to receive sham stimulation or tDCS with the anode over either the primary motor cortex (M1) or the dorsolateral prefrontal cortex (DLPFC), at 2 mA for 20 minutes on 5 consecutive days. All patients had an established diagnosis of FM according to the 1990 criteria of the American College of Rheumatology, had a mean pain score >e;4 on a 10-point visual analog scale (VAS) during the 2 weeks before the trial and a total tender point score of >e;20. "The primary motor cortex was chosen because extensive literature shows that stimulation (either invasive or noninvasive) of this area is associated with pain improvement," the authors write.

Stimulation of primary motor cortex but not other areas reduced pain

The tDCS was administered via a pair of saline-soaked sponge electrodes and a battery-driven constant current stimulator with a maximum output of 10 mA. "This device has a special feature that makes it particularly reliable for double-blind trials and was developed by our group, because we noted in our previous trials that patients try to look at the tDCS display during stimulation and encountered situations in which we had to hide the device from patients receiving sham treatment," the investigators write. The solution was to build in a switch that could be activated by the researcher to interrupt the electrical current while maintaining a sham display on the screen.

Clinical outcome was assessed using the VAS assessment for pain, the clinician's global impression (CGI), the patient's global assessment, and the number of tender points, the Fibromyalgia Impact Questionnaire, and the Short Form 36 (SF-36) Health Survey.

The investigators found that tDCS of the primary motor cortex reduced pain significantly more than either sham stimulation or stimulation of the DLPFC (P <.0001), and this effect was still significant 3 weeks after the completion of the 5 days of treatment (P = .004). There was a significant decrease in pain for the primary motor cortex group throughout the experiment.

Mean CGI scores after treatment were 2.51 for the primary motor cortex group, 3.11 for the DLPFC group, and 3.62 for the sham group. CGI scores are interpreted as 2 (much improvement), 3 (minimal improvement), or 4 (no change).

The change in tender point scores after 5 days of treatment showed significant improvement for the primary motor cortex patients versus the sham group (P = .008) but not for the sham versus DLPFC groups. Tender point scores on day 5 had decreased by 17.1 in the primary motor cortex group, by 11.8 in the DLPFC group, and by 2.3 in the sham group.

Neither depression nor anxiety were affected by treatment.

The main adverse effects were mild headaches, which were similar in the tDCS and in the sham groups. The authors note that tDCS was not associated with significant changes in cognitive function.

"The findings of the current study support the need for future investigations of novel neuromodulatory approaches for the treatment of fibromyalgia. Such studies should explore the duration of tDCS effects by performing longer-term follow-up evaluation and also by using different parameters of stimulation," the authors conclude.
 
FM paradigm shift

In an accompanying editorial, Michael C. Hsu, MD, and Daniel J. Clauw, MD, agree.² They write, "The results of this study if confirmed by other investigators, suggest an alternative mode of therapy for patients with fibromyalgia or other central pain syndromes." They also write, "The study also highlights the rapid movement toward neuromodulatory treatment of chronic pain, which requires a paradigm shift in how we think of chronic pain and its management."

Dr. Clauw, who is professor of medicine in the division of rheumatology and director of the Chronic Pain and Fatigue Research Center, at the University of Michigan, Ann Arbor, told CIAOMed, "This study supports the notion that fibromyalgia is a "central pain" syndrome, because stimulation of certain (but not any) region of the brain leads to an analgesic response."

"This absolutely can be used in clinical practice, and may turn out to be a very useful adjunct for the treatment of fibromyalgia," Dr. Clauw added.

References

1. Fregni F, Gimenes R, Valle AC, et al. A randomized, sham-controlled, proof of principle study of transcranial direct current stimulation for the treatment of pain in fibromyalgia. Arthritis Rheum. 2006;54:3988–3998.
2. Hsu MC, Clauw DJ, A different type of procedure for a different type of pain (editorial). Arthritis Rheum. 2006;54:3725–3727.